Interview with Prof. Werner Lang, Chair of Energy-Efficient and Sustainable Building and Planning

"We have no other choice but to build sustainably"

Prof. Werner Lang's objective is constructing residential buildings with a positive ecological footprint. In this interview he explains how this can be achieved and why energy efficiency means much more than just good thermal insulation.

Prof. Werner Lang on the roof of the Oskar-von-Miller-Forum in Munich.
Prof. Werner Lang on the roof of the Oskar-von-Miller-Forum in Munich. (Image: A. Eckert / TUM)

How strong is the impact of construction and habitation on the environment?

Werner Lang: The construction sector is responsible for approximately 40 percent of CO2 emissions and energy consumption and for well over half of the refuse produced. Energy consumption and in particular use of materials is enormous in construction. We have to manage these resources more efficiently.

Where can we make adjustments in order to reduce negative impacts on the environment?

Lang: The first aspect is energy efficiency: Buildings should be built in a way that requires a minimum possible reliance on fossil energies. However, other aspects play an even more decisive role in sustainability, for example the environmental impact of a particular building material or a certain building process. Ecologically sound construction means that our construction activities pose the smallest threat possible to the ecological balance.

Why is the way a building is constructed more significant for the environment than energy efficiency is?

Lang: Take for example a passive house. The energy consumed in operating the house is 15 kilowatt hours per square meter each year. That's a relatively small amount. Buildings from the 1970s consume from around 250 to 300 kilowatt hours per square meter each year. But the energy needed to construct the passive house is much higher than for conventional buildings. More thermal insulation is required, and the building infrastructure is more complicated. We use more materials in construction, and eventually the question arises: At what point do I have to invest more energy in construction than I'm saving during subsequent operations? So it makes good sense to consider how the building itself can produce as much energy as possible throughout its lifetime, for example using photovoltaics. If this is successful, then buildings can actually have a positive ecological footprint.

Students from your institute built a house like that in the US "Solar Decathlon" competition.

Lang: Two years ago the students joined with the University of Texas to formulate a concept for such a house in the competition. They planned a building that generates enough energy to power itself as well as an electric car, that is highly flexible, and that even allows for the redensification of our cities. In addition we wanted to show that closed water circuits can be created and food can be grown on the premises. But that was a little too ambitious for the short period of time available in the competition. The team won fourth place with the NexusHaus, a great accomplishment.

Do you think sustainable construction will establish itself? 50 years from now will we all be able to live in super-houses with positive energy footprints?

Lang: The effects of climate change are already costing thousands of lives in coastal regions and elsewhere, and are causing extreme weather events resulting in considerable economic damage in Central Europe. I believe we can't afford not to build sustainably. We can't do anything that doesn't actively contribute to stabilizing our climate. At the same time we have to search intensively for measures to accommodate ongoing climate change. One example here is making urban areas comfortable to inhabit in spite of the rising frequency of hotter and drier summers. Ultimately we have to take topics such as energy efficiency and specifically adaptation to climate change very seriously, and the time to act is now. This is also the objective pursued by the TUM's Center for Urban Ecology and Climate Adaptation (ZSK). The Center's task is to develop guidelines which put urban planning authorities in a position to be able to make the right decisions for tomorrow.

What is the concept underlying the Center for Urban Ecology and Climate Adaptation?

Lang: At least since the extreme summer of 2003, but also in the subsequent summers, the consequences of climate change have become more and more visible. The topic of energy efficiency and thus the reduction of CO2 emissions has received increasing attention, there has been discussion about thermal insulation thicknesses and on the correct legislation on construction activities, the right standards and so forth. But these discussions have completely ignored the fact that climate change is also changing the requirements placed on buildings. Thus I design and erect a building and completely overlook the fact that the building will be here for 60 years. I ask myself questions such as: Are we already insulating too much? Couldn't it be possible that cooling energy requirements will rise in the years to come? That means the energy I save on heating in winter will go right down the drain in the summer because my building is so well insulated that there's no way for me to get the heat inside the house to dissipate. It became clear to me that we need research to find out how the climate is developing and how we should respond. In the context of these considerations, the Bavarian State Ministry of the Environment and Consumer Protection placed a request with the Technical University of Munich. The issue was the pursuit of a more integrated approach to climate change. It was clear to me that we can't do this alone in the building sector. I spoke with Prof. Stephan Pauleit about the topics urban ecology and green infrastructure and we came up with the idea of founding the Center together with the Ministry of the Environment. In the meantime there are five different research projects currently in progress there. The goal of the Center is to leverage synergy effects between projects and not to engage in isolated individual research.


Prof. Dr.-Ing. Werner Lang
Technical University of Munich
Chair of Energy-Efficient and Sustainable Building and Planning
+49 (89) 289 - 23990

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